1. Field of the Invention
The present invention relates to a structure of an electro-mechanical vibration transducer used as an apparatus for producing a body-sensible sound vibration by an electric signal in a low sound range.
2. Description of the Related Art
A so-called body-sensible sound vibration, such as a vibration feeling felt as vibration of a body by a sound pressure or a vibration feeling felt through a floor surface or the earth, is used not only for audio to increase a heavy low sound feeling but also for an effective sound for, for example, a simulation or virtual reality to enable realistic presence to be reproduced by a documentary sound of an explosion sound, an engine sound, or the like which is accompanied by a vibration feeling or impact feeling. Moreover, its effects are expected in various fields, for example, in application to a music therapy utilizing a relaxation effect by the body-sensible sound vibration, and further, in usage with the object of acceleration of fermentation/maturation of liquor, improvement of quality, etc.
There has been an electro-mechanical vibration transducer, which is an apparatus for producing a body-sensible sound vibration which has been conventionally devised and used.
The electro-mechanical vibration transducer is structured such that a gap is formed between a magnetic pole and a column portion of a yoke, a coil wound around a coil frame is disposed in the gap, and a vibration is obtained by a magnetic interference action produced between a magnetic force generated at the coil by an electric signal and a magnetic force generated at the magnetic pole. In the following, with reference to FIG. 6, an example of a conventional electro-mechanical vibration transducer will be described.
As shown in FIG. 6, a case main body of the electro-mechanical vibration transducer is made up of frames 602 and 603 each having a plate-like section. Plate-like flange portions 604 and 605 extending in the horizontal direction are disposed at opening peripheral portions of the frames 602 and 603, and the frame 602 and the frame 603 are combined by abutting the flange portions 604 and 605 against each other in the state where the opening portions are made opposite to each other.
An outer peripheral fringe 607 of an annular damper 606 (what is formed by boring a plate-like epoxy material) made of an elastic material is held between the flange portions 604 and 605 of the frames 602 and 603, and an inner peripheral fringe 608 of the damper 606 extends horizontally in the direction opposite to the flange portions 604 and 605, that is, the inward direction of the frames 602 and 603.
A yoke 609 disposed in a case main body 601 is made up of a bottom plate 610 having a column portion 611 at its center and an annular top plate 612. An annular magnetic pole 613 is fixed to the bottom plate 610 in the state where it is loosely fitted to the column portion 611. The top plate 612 is attached to the magnetic pole 613, and a magnetic annular gap 616 is formed between an inner fringe 614 of the top plate 612 and an outer fringe 615 of the column portion 611 of the bottom plate 610. A magnetic circuit having the gap 616 is made up of the bottom plate 610, the magnetic pole 613, and the top plate 612.
For the purpose of supporting the yoke 609 in the case main body 601, the inner peripheral fringe 608 of the damper 606 is fixed to a stepped portion 621 formed of an outer fringe of the top plate 612 and an end surface of the magnetic pole 613, and the case main body 601 and the yoke 609 are structured to be relatively displaceable through the damper 606.
An opening 617 is formed at the center portion of the frame 602, a cylindrical coil frame 619 is fixed to the opening 617, that is, the inner peripheral fringe of the frame 602, and a coil 620 wound around the coil frame 619 is disposed in the gap 616. A plate 618 is fixed to the upper surface of the frame 602 so as to cover the opening 617.
In the thus structured electro-mechanical vibration transducer, by applying an electric signal generated by power amplification of a sound signal through a low pass filter to the coil 620, a magnetic interference action produced between a magnetic force generated at the coil 620 and a magnetic force of the magnetic pole 613 causes the yoke 609 supported by the case main body 601 and the case main body 601 to relatively change through the damper 606, so that the body-sensible sound vibration is produced.
However, in the foregoing conventional structure, although it is desired to obtain high oscillation efficiency down to a signal of a further low frequency, stiffness of the damper beyond a certain degree is need to support a heavy yoke, so that the conventional structure is accompanied with difficulty in design to obtain sufficient performance at a low frequency.
Even if the conventional structure has the stiffness of the damper beyond a certain degree to support a heavy yoke, since the case main body and the yoke is always relatively displaceable, the damper can not support the heavy yoke in case where a large load such as vibration or impact is applied at the time of transportation of products, so that defect occurs in the products. In order to avoid this, it is necessary to further stiffen the damper, so that reproduction of a low frequency becomes more difficult, and there has been a defect in performance that it is forced to sacrifice vibration efficiency.
The present invention has been made in view of the above problem, and an object thereof is to provide an electro-mechanical vibration transducer which provides a lock key for preventing a relative displacement between a case main body and a yoke so that defect due to vibration or impact at the time of transportation of products can be prevented from occurring in the products.
In order to solve the above problem, according to a first aspect of the invention, in an electro-mechanical vibration transducer in which a magnetic gap is formed by a yoke having a magnetic pole, the yoke is supported in a case main body by a damper, a coil is positioned in the gap, and the yoke and the case main body are relatively displaceable, the electro-mechanical vibration transducer is characterized in that a projecting portion of a lock key is inserted between the yoke and the case main body.
According to a second aspect of the invention, in the electro-mechanical vibration transducer of the first aspect, the lock key inserted between the yoke and the case main body is detachably attachable.
According to a third aspect of the invention, in the electro-mechanical vibration transducer of the first or second aspect, the damper includes a plurality of annular dampers each having a different size, the annular dampers are concentrically provided, and the respective dampers are connected to each other through a thin plate connecting portion.
According to a fourth aspect of the invention, in the electro-mechanical vibration transducer of any of the first to third aspects, the damper is made of concentrical-annular dampers connected to adjacent ones or spiral damper, which is a conical shape in a non-load state, and upper end or lower end of the damper is connected to the center of load of the lower surface of the case frame or the yoke concentrically.